共查询到20条相似文献,搜索用时 62 毫秒
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《中学生理科月刊》1995,(3)
1.要想从已知等式解出a、b、c是不可能的.因此,应对待求值式进行适当的变换,把未知转化为已知或可知,然后再整体代入.由已知,得a-C=50.这是可知.__1,。,_,,、,,,_,,、,,_,、,,B巨rt一一>厂(。‘-2。b+b‘)+(b’-Zbc>卜c’)+(c‘-Zac+a‘)」+5—””—”2“”—————”--1,。,、,。,、,。、,,_一H(rt-b)’W(b-C)‘+(C-rt)‘」+52“”—一”-””—”。I,,__/二一二二二、,,__/二7二二二、,l-_,,l-,___一H「(25W/115)’+(25-Jll5)‘… 相似文献
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一、掌握要求1.了解铁的物理性质,生铁和钢的有关知识。2应用铁的化学性质。二、内容辅导1.铁的物理性质与化学性质。.物理性质:银白色固体,具有金属光泽,质软,有良好延展性。【〔I干燥空气中——稳定归氧气反应(潮湿空气中一锈。_J。__,,__…。。__点燃__Thl,,,___1纯净的氧气中——燃烧(3Fe+ZD,HHFe风)一D化学性质(‘—’””‘—‘——‘帆’““””一’——““‘U‘’IlrFe+ZHCI一FeCI,+H,平【B与酸反应(_.____“_二。IB”—”—一{Fe+H,SO。一FeS风十H。半Lt与CUSO。… 相似文献
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《中学生理科月刊》1994,(6)
一、填空题(每空4分,共40分):1.方程的解是;2.若(X+y-1)2=0,则y一,/;___,、_、20‘,,__3.方程(X’十打)一一一一一一8的解是——”———一H‘+3H—”“‘”“’4不等式卜一4入<9的整数解的和是__;5若X;、X。是方程X’-6X+4—O的响个根,则卜;-X;]一,X;’-X。’、;6.若一个一元二次方程的两个根分别是方程X’一SX+13一0的两个根的3倍,则这个一元二次方程是;7.若方程x’+x-6一O和方程x’一sx+m一0有一个公共根,则m一二、单项选择题(每小题5分,共20分):1.若方程kX’-4x+2… 相似文献
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高中数学中,常遇到求(x+l)(x+2)(x+3)…(x+n)展开式中x‘项系数问题,本文旨在探求上述展开式中X”-‘,X”-’项系数的求解公式,并给出证明。__‘__。、、,。、,。、。、,__、____..、___。l,定理1整式(x+l)(x+2)(x+3)…(x十n),(n>2)展开式中x”-’项系数是:去(n-1)n————————””—-”-—””’”一””-——”””—“’—”‘一—”“”————”24””(,l+l)(3n+2)证明1”n—2时,(x+1)(x+2)一x’+3x+2,x‘-‘一x”项系数显然是2,又7(2一1)·… 相似文献
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三角形内用和定理及其推论表明了三角形的内角之间、内角与外角之间的关系,这些关系对于解决有关三角形的角的问题有着很重要的作用.下面举例说明它在解题中的若干应用,供同学们学习时参考.一、求三角形内角的庭教。l、,。_。,_,、。。‘1例1已知凸ABC中./A一音/B.-,——————-——-2“-:/B一手/C.求全C的度数.。1—一7———、—————、,————解设/t”的度数为。,则/B的度数为之。/A的度数为:。、.”“?一“““”“’“”“”“q“””由三角形内用和定理得//1+/B+/t”一1800,即gi[… 相似文献
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在《相似形》这一章中,证明线段比例式(或等积式)是必须掌握的基本技能之一.那么,证明线段比例式(或等积式)有哪些基本思路呢?一、利用相似三角形证明利用相似三角形的对应边成比例是证明线段比例式的基本思路之一.例且如图l,在凸Me中力是跟上一点,且AC’。_。__、_ABBC。AB·AD.求证:s二失.-‘一‘——”-”’——”AC-CD“分析由相似三角形的定义可知,相似三角形的____,。__,,。。、_用肥__、_^.__对应边成比例,因此,欲证兰一9.只须证凸ABC一’”————————”“’——一’—“一… 相似文献
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高中代数下册《不等式》一节有这样一IQ+b_道例题:“若la<1,fo<l,则【;7----IC——v、——·”。l-l—“”-——’””“1+fo-l.”这是一个意义深刻的例题,下面介绍它的一个变式及应用.。。。,_、Q+bl_、。:变式苦W<1,I;=.----【<1,则^。、”。-—“”1+a0—“’”“la<1.、_。。^Q+b。fo-H证明令x一;=---,则a一f==.一。。、一1+ah’”“-1一分“而la<1,l一一<1,由例题得;b+(-*_,。。11_。15-------<1,即la<1.1+b(-)’—“”””‘一—““应用(19… 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献